Hydraulic control system for die pads in presses



Oct. 23, 1962 F. M. WILLIAMSON 3,059,914

HYDRAULIO CONTROL SYSTEM FOR DIE PADS IN PRESSES Filed June 13, 1960 INV EN TOR.

United States Patent Chice 3,059,914 Patented Get. 23, 15962 Pail Thisinvention relates to presses of the type employing a movable die pad anda hydraulic cushion for resisting movement of the die pad upon closingof the press and for returning the die pad to its extended position uponopening of the press. The invention is particularly dirooted to animproved hydraulic control system for controlling the movement of thedie pad.

In presses of the type described it is frequently desirable to provide acontrol system which will automatically increase the pressure on thepiston which is relied upon to move the die pad to its extended positionwhen the press is opened, thereby insuring that the work will bestripped from the die by the return movement of the die pad. Thisincreased pressure should also be made available for a long enough timeto insure that the work will be stripped from the die, and the presentinvention is directed to a hydraulic system of this type in whichclosing of an electrical circuit is effected by the downward stroke ofthe ram, the closing of the circuit actuating a booster cylinder whichincreases the pressure in the hydraulic cushion to return the die pad toits extended position, and to an improved hydraulic system to maintainthe electrical circuit closed for a suitable time interval so as toinsure stripping of the work from the die by the pressure pad.

It is an object of the present invention to provide an improved controlsystem for hydraulic pads in a press.

Another object of the invention is to provide a control system of thetype described incorporating therein a timedelay mechanism for insuringthat the die pad will efficiently strip the work from the die uponopening of the press.

Other and further objects of the invention will be apparent from thefollowing description and claims and may be understood by reference tothe accompanying drawing, which by Way of illustration shows a preferredembodiment of the invention and what I now consider to be the best modeof applying the principles thereof. Other embodiments of the inventionmay be used without departing from the scope of the present invention asset forth in the appended claims.

In the drawing:

FIG. 1 is a schematic sectional view of a hydraulically actuated die padand the controll system for the die pad; and

FIG. 2 is a fragmentary sectional View of a part of the control systemshown in H6. 1 and illustrating a different position thereof.

A press of the type with which this invention may be used includes a ramand an upper die 12 carrying a forming tool, punch or the like 14engageable with the work 16 upon the downward stroke of the ram. Thework is supported on a movable die pad 13 which is verticallyreciprocable within a fixed bolster 2%. The hydraulic cushion for thedie pad 18 consists of a piston 22 rcciprocable with a cylinder 24.

A booster cylinder 26 is provided with a large diameter portion 28 and asmaller diameter portion 30. A double ended piston 32 is arranged withinthe booster cylinder 26. The larger diameter end 28 of the cylinder isprovided with a passage 34 leading to a valve 36 by means of which theend 28 of the cylinder may alternately be connected to a source of airunder pressure through line 38 or to the exhaust line 40. The controlvalve 36 is operated by a solenoid 42. The pressure fluid such as oil issupplied to the upper end of the cylinder 30 from a supply tank 44through a line 46 and past check valve 48 to passages 50 and 52 whichcommunicate with the cylinder 30.

A passage 54 connects the hydraulic cushion cylinder 24 with the boostercylinder 30. A check valve 56 normally closes the communication betweenpassages 52 and 54. A passage 58 is connected into passage 54 and leadsto a bore 60 in a valve block 62. The upper end of the bore 60 is closedby a pressure relief valve 64 which is backed up by a spring 66 and anadjustable threaded screw 68 so that the pressure at which the valve 64will open may be adjusted. The bore 60* intersects a transverse bore 70in the valve block which communicates with the supply tank 44. A by-passconsisting of passages 72 and '74 provides a communication between thepassages 60 and 70 and the by-pass is normally closed by a check valve76.

The control system further includes a pump indicated generally at and latime-delay mechanism indicated at The pump includes a cylinder 84containing a piston 86 which is urged to the left, as viewed in FIG. 1,by a spring 88 which is disposed within a recess in the piston '86 andreacts against a block 90 which closes the other end of the cylinder 84.A passage 92 is provided between the left-hand end of the cylinder 84and the passage 60. The stroke of the pump piston 86 is regulated by itsengagement with a plunger 94, the position of which may be adjusted byan adjusting screw 96.

The time-delay device 82 includes a cylinder containing a piston 102provided with a recess 104 within which a plunger 106 is reciprocable. Aspring 108 located within a recess in the plunger 106 reacts between thepiston 102 and the plunger 106 tending to urge the plunger outwardly. Astronger spring 110 reacts against a collar 112 secured to the piston102 and urges the piston and the plunger carried thereby to the left tothe position shown in FIG. 2.

An electric switch 114 includes a movable contact carried by a pivotedarm 116 which is urged by a spring 118 in a "direction to open theswitch 114. The switch 114 is wired into the electric circuit for thesolenoid 4-2 and, when the switch 114 is closed by movement of theplunger 106, the solenoid will be energized to move the valve 36 to theposition shown in which the booster cylinder 28 is connected to a sourceof fluid pressure.

When the press closes, the die pad 18 moves downwardly against piston 22and such downward movement is resisted by the hydraulic cushion providedby the oil trapped in the system. The oil discharged from the cylinder24 is forced through lines 54 and 58 into chamber 60 and through passage92 into cylinder 84 where it reacts against the piston 86 to move thesame to the right against its stop 94.

The oil in the right-hand end of the cylinder 84 is forced out of suchcylinder through passages 120 into a passage 122, past check valve 124and through passages 126 and 123 into the left-hand end of the cylinder100 to move the piston 102 and the plunger 106 carried thereby to theright to close the switch 114 and energize solenoid 42. The oil in theright-hand end of the cylinder 100 is forced out through a passage 130,past a check valve therein and back to the passage 122 or through apassage 132 which is connected by a passage 134 with the bore 70 so asto be returned to the supply tank 44.

When the solenoid 42 is energized the booster piston 32 will be actuatedand oil under high pressure will be forced from the booster cylinder 30,past check valve 56 through passage 54 into the cylinder 24- to forcethe piston 22 and the pad 18 upwardly to strip the work from the die.Oil will also be forced through passages spacers U 58, 6t} and 92 intothe cylinder 84 to maintain the piston 36 against the stop 94.

The solenoid will remain energized until the plunger 1456 is returned toits left-hand position shown in FIG. 2, and return of the plunger 106and the piston 162 is delayed due to the oil trapped in the cylinder1th). The oil in the cylinder 160 escapes slowly through passages 128and 126, past a bleeder valve 140 and then through passages 132 and 134and bore 70 back to the supply tank 44-. The bleeder valve 140 is in theform of an adjustable screw which may "be adjusted to regulate the rateat which oil escapes from the cylinder 1%. The extent of the time delayis also determined by the amount of oil forced into the cylinder 100 andthis is in turn regulated by the extent of movement of the pump piston86. As the oil escapes from the cylinder 100, the piston it moves to theleft under the force of spring 111i), but the plunger 1% will remain inits extended position under the influence of spring 108 until the pistoni 02 reaches the end of its stroke at which time the collar 112 on thepiston engages a shoulder 142 on the plunger 106 to retract the plungeragainst spring 108 to open the switch 114. When the switch 114 is openedthe solenoid 42 is de-energized to connect the passage 34 to the exhaustline 40, whereupon the booster cylinder 30 will be filled With oil fromthe tank 44 through passage 46, past check valve 48 and through passages50 and 52, thereby returning the booster piston 32 to its loweredposition. During the time the solenoid is energized the high pressurewill be maintained within the cylinder 24. When the pressure isreleased, as described, the piston 86 is returned to its left-handposition, forcing oil from the left-hand end of cylinder 84 throughpassage 92, past bleeder valve 144 to passage 134 and bore '70 back tothe supply tank 44. The right-hand end of the cylinder 84 will be filledWith oil from the tank 44 through passages 134, 132 and 130, past checkvalve 146 and through passages 12.2 and 120.

The pressure relief valve 64 is normally closed and will open only whena predetermined pressure is exceeded either upon closing of the press orupon actuation of the booster piston to return the die pad 18 to itsextended position.

This application is a continuation-in-part of my prior copendin gapplication Serial No. 768,889, filed October 22, 1958, for HydraulicPress Ram Cushion.

While I have illustrated and described a preferred embodiment of myinvention, it is understood that this is capable of modification, and Itherefore do not wish to be limited to the precise details set forth butdesire to avail myself of such changes and alterations as fall withinthe purview of the following claims.

I claim:

1. in a press having a movable pressure pad engaged by the work so as tobe moved in one direction upon closing of the press and including ahydraulic cushion to resist such movement of said pad and to effectreturn movement of the pad upon opening of the press, said hydrauliccushion including a cylinder and a piston in said cylinder, a supply ofhydraulic fluid under pressure connected to said cylinder for biasingsaid piston therein to react against said pad, a control system forcontrolling the return movement of said pad, comprising a boostercylinder having a hydraulic fluid connection with said hydraulic cushioncylinder, a piston in said booster cylinder, a valve connected betweensaid booster cylinder and a source of pressure fluid for controllingactuation of said booster piston and adapted when open to supplypressure fluid to said booster cylinder so as to move said boosterpiston in a direction to increase the pressure in said hydraulic cushioncylinder to etfect return movement of said pad, a solenoid connected tosaid valve and adapted when energized to open said booster controlvalve, a normally open switch in the solenoid circuit and including amovable contact, a cylinder having a plunger therein, said movablecontact being movable with said plunger, a spring reacting on saidplunger in a direction to open said switch, a pump cylinder having apiston therein, means communicating said hydraulic cushion cylinder withsaid pump cylinder on one side of said pump piston to move the latter inone direction by hydraulic fluid discharged from said hydraulic cushioncylinder upon closing of the press, a passage connecting the cylindercontaining said plunger with said pump cylinder on the other side ofsaid pump piston, a one-way valve in said passage through whichhydraulic fluid is pumped from said pump cylinder into said plungercylinder to effect movement of said plunger against its spring to closesaid switch and effect actuation of said booster piston, a supply tankfor said hydraulic fluid, passage means communicating said plungercylinder with said tank, and a bleeder valve in said passage means forrestricting the flow of hydraulic fluid from said plunger cylinder todelay return movement of said plunger and thereby opening of saidswitch.

2. in a press having a movable pressure pad engaged by the work so as tobe moved in one direction upon closing of the press and including ahydraulic cushion to resist such movement of said pad and to effectreturn movement of the pad upon opening of the press, said hydrauliccushion including a cylinder and a piston in said cylinder, a supply ofhydraulic fluid under pressure connected to said cylinder for biasingsaid piston therein to react against said pad, a control system forcontrolling movement of said pad, comprising a booster cylinder having ahydraulic fluid connection with said hydraulic cushion cylinder, apiston in said booster cylinder, a valve connected between said boostercylinder and a source of pressure fluid for controlling actuation ofsaid booster piston, said booster piston when actuated being adapted toincrease the pressure in said hydraulic cu'stion cylinder to effectreturn movement of said pad, a cylinder having a plunger therein, aspring reacting on said plunger in one direction, means operable inresponse to movement of said plunger in the other direction foroperating said valve to actuate said booster piston, a pump cylinderhaving a piston therein, means communicating said hydraulic cushioncylinder with said pump cylinder on one side of said pump piston to movethe latter in one direction by hydraulic fluid discharged from saidhydraulic cushion cylinder upon closing of the press, a passageconnecting the cylinder containing said plunger with said pump cylinderon the other side of said pump piston, a one-way valve in said passagethrough which hydraulic fluid is pumped from said pump cylinder toeflect movement of said plunger in said other direction against itsspring to operate said valve and thereby eifect actuation of saidbooster piston, a supply tank for said hydraulic fluid, passage meanscommunicating said plunger cylinder with said tank, and a bleeder valvein said passage means for restricting the flow of hydraulic fluid fromsaid plunger cylinder to delay return movement of said plunger.

3. In a press having a movable pressure pad engaged by the work so as tobe moved in one direction upon closing of the press and including ahydraulic cushion to resist such movement of said pad and to eifectreturn movement of the pad upon opening of the press, said hydrauliccushion including a cylinder and a piston in said cylinder, a supply ofhydraulic fluid under pressure connected to said cylinder for biasingsaid piston therein to react against said pad, a control system forcontrolling movement of said pad, comprising a booster cylinder having ahydraulic fluid connection with said hydraulic cushion cylinder, abooster piston in said booster cylinder, a valve connected between saidbooster cylinder and a source of pressure fluid for controllingactuation of said booster piston and adapted when open to supplypressure fluid so as to move said booster piston use,

in a direction to increase the pressure in said hydraulic cushioncylinder to effect return movement of said pad, a cylinder having aplunger therein, means operably connecting said valve and plunger foropening said valve upon movement of said plunger in one direction andfor closing said valve upon movement of said plunger in the oppositedirection, means responsive to hydraulic fluid discharged from saidhydraulic cushion cylinder upon closing of the press to move saidplun'ger in said one direction, spring means biasing said plunger insaid opposite direction, a supply tank for said hydraulic fluid, passagemeans communicating said plunger cylinder with said tank, and a bleedervalve in said passage means for restricting the flow of hydraulic fluidfrom the said plunger cylinder to delay movement of said plunger in saidopposite direction thereby to delay closing of said booster pistoncontrolling valve.

4. In a press having a movable pressure pad engaged by the work so as tobe moved in one direction upon closing of the press and including ahydraulic cushion to resist such movement of said pad and to effectreturn movement of the pad upon opening of the press, said hydrauliccushion including a cylinder and a piston in said cylinder, a supply ofhydraulic fluid under pressure connected to said cylinder for biasingsaid piston therein to react against said pad, a control system forcontrolling movement of said pad, comprising a booster cylinder having ahydraulic fluid connection with said hydraulic cushion cylinder, abooster piston in said booster cylinder, a valve connected between saidbooster cylinder and a source of pressure fluid for supplying fluidunder pressure to said booster cylinder to move said booster piston inone direction thereby to increase the pressure in said hydraulic cushioncylinder, a valve actuating means operable in response to hydraulicfluid discharged from said hydraulic cushion cylinder upon movement ofsaid pad in said one direction to open said valve and eflect saidmovement of said booster piston, said valve actuating means including acylinder having a plunger therein, means operably connecting said valveand plunger for opening said valve upon movement of said plunger in onedirection and for closing said valve upon movement of said plunger inthe opposite direction, an inlet passage for said plunger cylinderthrough which pressure fluid is supplied to said plunger cylinder toeffect movement of said plunger in said one direction to open saidvalve, spring means urging said plunger in said opposite direction, asupply tank for said hydraulic fluid, passage means communicating saidplunger cylinder with said tank, and a bleeder valve in said passagemeans for restricting the flow of pressure fluid from said plungercylinder thereby to delay movement of said plunger in said oppositedirection.

5. In a press having a movable pressure pad engaged by the work so as tobe moved in one direction upon closing of the press and including ahydraulic cushion to resist such movement of said pad and to effectreturn movement of the pad upon opening of the press, said bydrauliccushion including a cylinder and a piston in said cylinder, a supply ofhydraulic fluid under pressure connected to said cylinder for biasingsaid piston therein to react against said pad, a control system forcontrolling movement of said pad, comprising a booster cylinder having afluid pressure connection with said hydraulic cushion cylinder, abooster piston in said booster cylinder, a booster control valveconnected between said booster cylinder and a source of pressure fluidfor controlling actuation of said booster piston and adapted when opento supply pressure fluid for moving said booster piston in a directionto increase the pressure in said hydraulic cushion cylinder to effectreturn movement of said pad, a solenoid connected to said control valveand adapted when energized to open said booster control valve, anormally open switch in the solenoid circuit and including a movablecontact, a time-delay device including a con trol cylinder having aplunger therein, said movable contact being movable with said plunger,means responsive to hydraulic fluid discharged from said hydrauliccushion cylinder upon closing of the press to efrect movement of saidsplunger in one direction to close said switch and elfect actuation ofsaid booster piston, spring means urging said plunger in the oppositedirection to open said switch and thereby close said valve anddeenergize said booster, a supply tank for said hydraulic fluid, passagemeans communicating said control cylinder with said tank, and a bleedervalve in said passage means for restricting the flow of pressure fluidfrom said control cylinder to delay movement of said plunger in saidopposite direction thereby to delay opening of said. switch.

6. In a press according to claim 5, said time-delay device including apiston reciprocable in said control cylinder, said plunger beingreciprocable within said piston, a first spring reacting between saidlast-named piston and plunger and urging said plunger in said onedirection, a second spring reacting in said opposite direction betweensaid control cylinder and said piston therein, said second spring beingstronger than said first spring, said piston in said control cylinderbeing movable in said opposite direction without corresponding movementof said plunger, and cooperating means on said last-named piston andplunger operable for moving said plunger with said piston only as thelatter reaches the limit of its movement in said opposite directionwhereby said switch remains closed until the pressure fluid escapes pastsaid bleeder valve.

7. In combination with a press having a movable pressure pad engaged bythe work so as to be moved in one direction upon closing of the pressram and a hydraulic system including a hydraulic cushion to resist suchmovement of said pad and to effect return movement of the pad uponopening of the press ram, said hydraulic cushion including a cylinderand a piston therein, a tank of hydraulic fluid under relatively lowpressure having a hydraulic fluid connection to said cylinder forsupplying hydraulic fluid to said cylinder for biasing said pistontherein to react against said pad, a pressure relief valve in saidconnection which resists the displacement of hydraulic fluid from saidcylinder upon closing of the press ram, a fluid pressure actuatedbooster having a hydraulic fluid connection with said tank and with saidhydraulic cushion cylinder and operable when actuated to increase thepressure of the hydraulic fluid in said hydraulic cushion cylindersubstantially above the pressure in said supply tank, to effect returnmovement of said pad, and means operable upon closing of the press ramto control the supply of fluid pressure to said booster so as to actuatesaid booster upon closing of the press ram and to maintain the supply offluid pressure to said booster for a predetermined time during theopening of said press ram.

8. In combination with a press having a movable pressure pad engaged bythe work so as to be moved in one direction upon closing of the pressram and a hydraulic system including a hydraulic cushion to resist suchmovement of said pad and to eifect return movement of the pad uponopening of the press ram, said. hydraulic cushion including a cylinderand a piston therein, a tank of hydraulic fluid under relatively lowpressure having a hydraulic fluid connection to said cylinder forsupplying hydraulic fluid to said cylinder for biasing said pistontherein to react against said pad, a pressure relief valve in saidconnection which resists the displacement of hydraulic fluid from saidcylinder upon closing of the press ram, a booster having a hydraulicfluid connection with said hydraulic cushion cylinder and operable uponclosing of the press ram to increase the pressure of the hydraulic fluidin said hydraulic cushion cylinder'substantially above the pressure insaid supply tank to effect return movement of said pad upon opening ofthe press ram, and means operable upon closing of the press ram inresponse to closing of the press ram to actuate said booser and tomaintain said booster operable for a predetermined time during theopening of said press ram.

9. In a press having a movable pressure pad engaged by the work so as tobe moved in one direction upon closing of the press ram, a hydrauliccushion reacting against said pad to resist such movement of said padand to effect return movement of the pad upon opening of the press ram,said hydraulic cushion including a cylinder and a piston therein, a tankcontaining hydraulic fluid under pressure, a booster cylinder, a fluidconnection between said tank and booster cylinder, a check valve in saidconnection past which hydraulic fluid flows from said tank to saidbooser cylinder, a passage connecting said booster cylinder and saidhydraulic cushion cylinder, a piston in said booster cylinder, a controlvalve connecting said booster cylinder to a source of pressure fluid andadapted when open to supply pressure fluid to actuate said boosterpiston in a direction to force the hydraulic fluid in said boostercylinder through said passage to said hydraulic cushion cylinder toincrease the pressure in the latter cyl- 20 inder to effect returnmovement of said pad, control means connected to said control valve andactuated by the press for opening said control valve to actuate saidbooster piston at a predetermined time during each cycle of the press, anormally closed valve in said passage, including a reciprocable valvemember and a spring biasing said valve member to a position closing saidpassage, the opposite sides of said valve member being exposed to thepressure in said tank so that both sides of said valve member arenormally subjected to the pressure of the hydraulic fluid in said tank,said valve member being movable against said spring to open said passageupon actuation of said booster piston, a return line through whichhydraulic fluid flows from said hydraulic cushion cylinder to said tankupon closing of the press, and a pressure relief valve in said returnline providing resistance to movement of said die pad and adapted toopen when the pressure in said hydraulic cushion cylinder exceeds apredetermined pressure.

References Cited in the file of this patent UNITED STATES PATENTS1,433,116 Beyer Oct. 24, 1922 2,890,669 Williamson June 16, 19592,933,307 Williamson Apr 19, 1960

